Fish oil supplements lying on table

Is fish oil a blood thinner?

Medically reviewed on January 23, 2023 by Morgan Spicer, Medical Communications Manager. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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You’ve probably heard the buzz about fish oil, omega-3s, and how they may be able to support your health. But for those with health conditions or who take medications, it’s vital to know how new supplements will interact with them in your body before trying them for yourself.

Fish oil contains docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are two essential omega-3 fatty acids. Omega-3s make up the cell membranes throughout your body. In turn, they support your body’s optimal health and functioning [1].

Your body doesn’t produce enough EPA or DHA on its own. As a result, you must consume these regularly through foods high in omega-3 or through supplementation. Fish oil supplements can help you consume adequate omega-3s without altering your diet. But if you’re dealing with a health condition or take certain medications, you may be wondering, “Is fish oil a blood thinner?”

In this article, we’ll explain fish oil’s impact on your blood and examine how it may react with blood thinning medications.

How does fish oil affect the blood?

Despite any myths you may have heard, standard amounts of fish oil don’t thin the blood [2]. A meta-analysis of six studies showed that fish oil doesn’t increase bleeding levels (a sign of thin blood) [2, 3].

These studies looked at daily fish oil dosages ranging from 500 milligrams to 10,000 milligrams [4]. However, most fish oil supplements only contain between 100 and 1,000 milligrams of omega-3 fatty acids [5].

With this evidence in mind, you can safely take regular doses of fish oil supplements without worrying about any blood-thinning effects.

How much fish oil thins blood?

In order to experience blood-thinning effects, you would have to consume extremely high amounts of fish oil. Research has shown that taking over 10,000 milligrams of fish oil may thin the blood [4], though not necessarily. Fortunately, no supplements contain even close to this amount.

With this in mind, saying that fish oil is a blood thinner is as silly as stating that drinking water is lethal—at excessive doses, anything can be dangerous.

Why does this myth exist?

The myth that fish oil is a blood thinner started back in the 1970s. It stems from the fact that omega-3 fatty acids can interact with platelets [5], which are blood cell fragments that facilitate blood clotting.

While fish oil may help prevent blood clots [6], it doesn’t do so by thinning the blood. Instead, it helps prevent clots by making your blood less sticky.

If you’re at risk of blood clots, a fish oil supplement may be able to help reduce your risk, along with other medical interventions and healthy lifestyle changes [7]. The American Heart Association has recommended fish oil supplements to people with cardiovascular disease for over 20 years [8].

What are blood thinners and what do they do?

If fish oil isn’t a blood thinner, you may be wondering what is. Blood thinners are medications that prevent blood clots from forming [9]. They can’t break up existing blood clots, but they can keep them from growing.9 Blood clots are dangerous because, left unchecked, they can lead to strokes and heart attacks [9].

There are two types of blood thinners on the market [9]:

  • Anticoagulants – Anticoagulants, such as warfarin or heparin, slow down your body’s blood clotting process.
  • Antiplatelets – Antiplatelets, such as aspirin or clopidogrel, keep your platelets from clumping together and creating new clots.

Blood thinners may be prescribed to people with heart disease, blood vessel disease, congenital heart defects, or atrial fibrillation. They may also be given to patients who have undergone surgery [9].

Can I take omega-3 supplements and blood thinners at the same time?

If you’re currently taking blood-thinning medication, you should consult with your healthcare provider before you take any new supplements, including fish oil. They may tell you to avoid certain medications and supplements.

The reason? Even if they don’t act as blood thinners themselves, some drugs and supplements can change the way that your blood thinners work [10], including [11]:

  • Fish oil
  • Some antidepressants
  • Certain anti-inflammatory drugs
  • Some herbal supplements
  • Cranberry juice
  • Alcohol
  • Vitamin K

Your healthcare provider may also ask you to halt your fish oil supplementation in the weeks leading up to surgery, though this may be an exercise of extreme caution. After all, a 2018 study in Circulation showed that high doses of fish oil didn’t increase perioperative bleeding [12].

Everlywell: get high-quality supplements sent to your doorstep

In summary, fish oil won’t thin your blood unless you take absurdly high amounts of it. However, if you’re on blood thinners, you may want to speak with your healthcare provider before taking fish oil or any other supplements.

If you want to increase your omega-3 levels safely, Everlywell can help. Our Omega-3 Fish Oil Supplements contain a dose of 1,000 milligrams of omega-3s. Since they’re third-party tested, you can rest assured that you’re getting the very best quality DHA and EPA.

Your first order will include a 30-day supply of supplements delivered right to your door. By subscribing to our monthly delivery service, you can save 10% on your subsequent orders. And don’t worry—you can cancel your subscription at any time.

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  1. Omega-3 fatty acids & the important role they play. Cleveland Clinic. URL. Accessed January 4, 2023.
  2. Office of dietary supplements - omega-3 fatty acids. NIH Office of Dietary Supplements. URL. Accessed January 4, 2023.
  3. Thrombocytopenia: Symptoms, stages & treatment. Cleveland Clinic. URL. Accessed January 4, 2023.
  4. Fish oil LC-PUFAs do not affect blood coagulation parameters and bleeding manifestations: Analysis of 8 clinical studies with selected patient groups on omega-3-enriched medical nutrition. Define_me. URL. Accessed January 4, 2023.
  5. McEwen BJ;Morel-Kopp MC;Chen W;Tofler GH;Ward CM; Effects of omega-3 polyunsaturated fatty acids on platelet function in healthy subjects and subjects with cardiovascular disease. Seminars in thrombosis and hemostasis. URL. Accessed January 4, 2023.
  6. Fish oil. Mayo Clinic. URL. Published December 8, 2020. Accessed January 4, 2023.
  7. Alyson Kelley-Hedgepeth MD. Omega-3 fatty acids and the heart: New evidence, more questions. Harvard Health. URL. Published March 24, 2021. Accessed January 4, 2023.
  8. Fish and omega-3 fatty acids. URL. Published July 20, 2022. Accessed January 4, 2023.
  9. Blood thinners | anticoagulants. MedlinePlus. URL. Accessed January 4, 2023.
  10. 5 things to know about omega-3s for heart disease. National Center for Complementary and Integrative Health. URL. Accessed January 4, 2023.
  11. Warfarin side effects: Watch for interactions. Mayo Clinic. URL. Published February 22, 2022. Accessed January 4, 2023.
  12. Fish oil and perioperative bleeding. Circulation: Cardiovascular. URL. Accessed January 5, 2023.
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